1. Field of the Invention
The present invention pertains to the art of hauling cargo from place to place and more particularly to trailers used to haul either discrete cargo that is typically transported on a flat bed and loose bulk cargo such as crushed stone or sand that is typically transported in a hopper.
2. Discussion of the Prior Art
In the past large discrete items of cargo have been traditionally transported on flatbed trailers and loose bulk cargo has been transported in trailers that have hoppers. Since such trailers are designed to transport only one type of load, often the trailers made a trip one-way loaded and make a return trip empty. Traveling in a non-loaded condition is wasteful and considered undesirable because of the large cost of fuel and labor costs associated with moving an empty trailer.
In response to this problem Schmidt et al have proposed in U.S. Pat. No. 4,082,357 to start with a box-type semi-trailer and adding a grate type floor and hoppers. The patent then teaches a relatively complicated conversion system which supposedly allows an operator to convert the trailer from a hopper configuration to a box configuration. Numerous walls and partitions must be moved and sealed to change the trailer from one configuration to the other.
Sentle, Jr. et al. have proposed a dual purpose trailer body for converting between a first configuration for handling freight of a bulk nature such as coils of steel or paper and to a second configuration for handling comminuted material such as dolomite or grain. The patent teaches moving large floor panels from a horizontal position to a vertical position to convert the trailer from the first to second positions.
Apparently the difficulties involved with these types of convertible trailers in terms of the effort required to convert them from one configuration to another has been so great that none of them are currently in mass production except for a trailer produced by Western Trailers. Even the Western Trailer unit has so many problems with the conversion process that divers will only convert them seasonally. The trailers still often travel in a non-load condition because of the labor and safety issues involved with converting the trailer is so great it is cheaper to run the trailer empty.
Also in all of the above-mentioned convertible trailers and indeed for flat bed trailers generally there is the additional problem of the trailers having weakness in the longitudinal direction that allows undesirable longitudinal flexing.
Based on the above, there is a need in the art for a trailer that can transport multiple types of loads and does not have to be converted from one mode to another and additionally reduces longitudinal flexing.